The present invention relates generally to marine jet propulsion units, and specifically to relatively higher-powered, inboard mounted marine jet propulsion units having indirect drive systems.
The popularity of jet propulsion units for powering small marine craft such as jet skis, as well as larger pleasure boats continues to increase for many reasons. These jet propulsion units are being used as replacements for propeller driven outboard or inboard marine motors. Some of the more significant advantages of jet propulsion units include the lack of a depending gear case, which allows the craft to virtually "float" above the water surface at high speed, thus enabling the operator to make tight turns while maintaining the boat in a generally horizontal or level orientation. Another advantage of marine jet propulsion units is the absence of an exposed propeller which enables the craft to be operated in shallower water without fouling.
Even though the use of jet propulsion units enables watercraft to be operated in shallower water, such units do exhibit the possibility for fouling and such fouling generally occurs as a result of taking in weeds or other debris into the intake of the unit.
It is a common design for such jet propulsion units to have a grill located on the intake so that large objects cannot enter the intake passage and eventually reach the impeller, but it is not entirely possible to keep weeds and other smaller debris from doing so. It is also common that debris may accumulate on the outside of the grill and eventually reduce or almost stop the flow of water through the propeller unit which will greatly affect the performance of the unit. If the debris enters the intake passage, it will generally pass through to the impeller where it may stop the impeller and kill the engine.
Assuming that debris does enter the intake and obstruct the main passage and necessitate that it be cleaned out, the access to the interior passage and impeller is often difficult in many prior art designs. Since the power head and gear housing are generally inside of the watercraft, there are conventional designs which have an access or door inside of the watercraft which can be removed or opened and the debris can be cleaned out. There are often two problems associated with this design. One is that since the power head and gear housing are inside of the watercraft, there may not be much room in which a person can maneuver to clean out the debris. Also, since the problem will probably result during operation, the motor may be hot and provide a safety hazard to someone attempting to do a clean out operation.
Accordingly, it is a primary object of the present invention to provide a marine propulsion unit having an impeller and main water passage that is accessible from outside of the watercraft.
A related object is to provide such a marine propulsion unit which is easily accessible from outside of the watercraft and which provides a generous accessibility to the impeller which promotes cleaning thereof.
Another related object lies in the provision for separating the drive shaft of the impeller from the impeller itself which can greatly facilitate the removal of debris, particularly if the debris comprises wire, elongated plant material or the like, which may be wound on the drive shaft and/or the impeller.
Still another object of the present invention is to provide such a marine propulsion unit which has an impeller housing located outside of the transom of the watercraft, a portion of which housing is adapted to be separated from the remainder thereof to expose the inside the housing where the impeller is located.
Still another object of the present invention lies in the provision for rotatably journaling the impeller within the impeller housing so that the drive shaft which is connected to the gear train in the gear housing can separate from the impeller when the separable portion of the impeller housing is moved away from the transom.
Yet another object of the present invention is to provide an alternative embodiment whereby the separable portion of the impeller housing can be pivoted away from the transom by virtue of a hinged connection on one side of the impeller housing.
Another object of the present invention is to provide a simple and convenient apparatus for flushing the water cooling system of the power head that is possible as a result of the separability of the portion of the impeller housing.
A further object of the present invention is to provide a pressure relief apparatus for controlling the amount of coolant diverted to the power head by the impeller.
These and other objects will become apparent upon reading the following detailed description while referring to the attached drawings.